Power supply



FIG. 1 is a top view of a power supply showing the new design;

FIG. 2 is a left side view;

FIG. 3 is a front view;

FIG. 4 is a bottom view;

FIG. 5 is a right side view; and,

FIG. 6 is a rear view. 

The ornamental design for a power supply, as shown and described. 